Id not flush prior to flowering.
#1 thing is there No Reason to change nutrient ratios during flowering.
The plant just needs ever increasing amounts of everything up to a certain point. They take your money saying one needs different nutrients for flowering vs veg ect.
From what little I know, tissue analysis says weed likes a 1-1-2 ratio. Specifically a 19.5-20-39, and the only thing changed during life is ever increasing amounts of PPM, and a boost of P_K, and Epsom Salts at certain points, and them cut back in the last weeks of flowering. To much fert hinders ripening, and can cause excess leaves. The sulfur in Epson Salts increases terpene production in the last stages.
I like Hydro Gardens-Chem Gro fertilizer which is specifically made for weed, and the company has been making plant specific fertilizer since the 1970s, and greenhouses, and supplies since the 1960s.
Base formula is 4-20-39
15.5-0-0 Calcium Nitrate which is 18% Calcium vs 3%-5% for Cal Mag, and I like the idea of getting the Magnesium, and Sulfur together via the Epsom Salts. Easier to supply sulfur, and they get Nitrogen, and Calcium from the Calcium Nitrate
Say in a normal 8 weeks flowering strain the feed schedule is ever increasing PPM of everything whilst keeping the base ratio of 1-1-2 up until week 6 of flowering. Weeks 7-8 food gets cut in half, but not eliminated.
In weeks 2.5-5 they can benefit from a 0-52-34/MPK Boost, and weeks 5-6 can benefit from an Epsom Salts boost. Weeks 7-8 they get cut back.